TM 5-2410-241-23-1
0011
IMPLEMENT AND STEERING HYDRAULIC SYSTEM CONTINUED
Control Valve (Ripper Lift)
00011
When the machine is equipped with a bulldozer and a ripper, the ripper lift control valve is the fourth valve in the
valve stack. The ripper lift control valve controls the raising and lowering of the ripper. The control valve is equipped
with these components: makeup valve, resolver, pressure limiter valve, load check valve, and valve spool.
The ripper lift control valve is spring centered. The control valve spool is a closed center spool and a pilot operated
spool with three positions: RAISE, HOLD, and LOWER. The spring keeps the valve spool in the HOLD position
when the ripper lift control valve is not active. Movement of the spool is controlled by the pilot control system which
connects the ripper control lever to the valve spool.
The resolver is a double check valve. The functions of the resolver and of the control valve spool are described in
the sections on positions of the control valve. The descriptions of the functions of the makeup valve, pressure
limiter valve, and the load check valve are in the following separate sections.
a. Load Check Valve
00011
The load check valve prevents reverse oil flow in the ripper lift cylinders, which can cause cylinder drift or load loss.
The load check valve does not open until pump oil pressure in the chamber overcomes the force of the spring for
the load check valve and of the cylinder oil pressure in the passage.
b. Makeup Valve
00011
The makeup valve is in the head end of the lift circuit. The makeup valve opens when cylinder oil pressure in
passage drops 2 psi (14 kPa) below the return oil pressure in the outlet passage. The makeup valve adds return oil
in outlet passage to cylinder oil in passage. The additional oil prevents cavitation (vacuum) in the lift cylinders.
c. Pressure Limiter Valve Operation
00011
The pressure limiter valve is used in the ripper lift control valve in order to limit the pressure to the lift circuit. The
pressure setting of the pressure limiter valve is 3,300 45 psi (22,750 300 kPa).
When the ripper lift control valve is in an operating position, cylinder oil flows through the passage and the oil
becomes signal oil. Signal oil flows to the chamber then to the resolver.
When the signal oil pressure in spring chamber #2 reaches approximately 3300 psi (22,750 kPa), the spool in
pressure limiter valve moves from the valve seat. Oil is sent through the outlet passage to the tank.
The signal oil causes the flow control valve to move to the right. The flow of pump oil to the lift circuit decreases
until the pressure of the cylinder oil decreases.
Basic Valve Operation
00011
When the control valve spools are in the HOLD position, pump oil flows to the inlet passage. This passage is
common to all sections of the valve stack and this passage has no outlet. Since all the valve spools are in the
HOLD position, pump oil fills the parallel oil passages of the control valves. The pump maintains oil pressure at
525 psi (3,600 kPa). Signal oil passage, chamber #1, and resolver are drained. Rod end passage, head end
passage, and chamber #1 are blocked.
0011-38
